The present invention relates to packaging machines, in particular, automatic packaging machines for packaging products such as rolls of paper, holding them together in the form of a pack, using a sheet of wrapping material which is wound and folded around the product and sealed over itself.
In packaging machines of the above-mentioned type, packaging is effected by feeding the individual products or groups of products one after another along a forming line, on which the products, between pusher elements at stepped intervals and mobile along the forming line, move forward with intermittent motion, passing through a series of operating stations, in which packaging is effected.
The operating stations respectively envisage: the infeed into the machine of products topped by a sheet of wrapping material, for example a plastic film; winding of the sheet of wrapping material around the products and overlapping of the opposite edges of said material underneath the products; the formation on the sheet of wrapping material of two pairs of first, vertical flaps, folded against the products; the formation of two pairs of second flaps; sealing of the edges of the sheet of wrapping material underneath the pack; folding of the pairs of second flaps against the pack and, finally, sealing of the pack by sealing the flaps to the sheet of wrapping material.
The present invention concerns, in particular, an automatic machine, of the above-mentioned type and corresponding with the preamble to claim 1, for effecting the above-mentioned product packaging.
The machine comprises a forming line for the wrapper, along which the three operating stations are arranged one after another above a sliding surface for the products, which are fed with a stepping motion along the surface by the mobile pushers. The first operating station of the forming line co-operates with a lift, located below the product sliding surface and vertically and alternately mobile between a lower level, at which it receives the products on its loading table, and a raised level, at which it places the products on the forming line sliding surface and inserts them between the pusher elements with a sheet of wrapping material laid on top of them. The sheet hangs down on both sides of the pack, with its vertical folds positioned between the products and the pusher elements. The first operating station also comprises a horizontal-plane folder and counter-folder, located below the sliding surface and on either side of the lift. The folder and counter-folder are alternately mobile parallel with the product sliding surface, from a first, open end position, in which they allow the lift loading table to move freely towards the product sliding surface, to a second, closed end position, in which they are brought together above the lift loading table in such a way that they gradually take the products from it, supporting them on the sliding surface and simultaneously winding the opposite edges of the sheet until the edges overlap underneath the products. The machine also comprises two pairs of vertical-plane folders which are parallel with one another and with the forming line, located on either side of the products at a distance corresponding to the depth of the pack, and are mobile opposite one another alternately between two end positions. In a first, non-operating, end position, the vertical-plane folders are outside the width dimension of the pack; in the second, operating, end position, they are, in contrast, brought together. During the movement necessary to reach the second, operating position, the vertical-plane folders intercept vertical edges of the sheet, fold them about vertical fold lines and form pairs of first, vertical flaps, which are pressed against the products, then form pairs of second, horizontal flaps located on either side of the vertical-plane folders. The second station comprises two pairs of fixed folders, located on either side of the forming line and at a vertical distance from one another which depends on the height of the pack of products, and a horizontal distance from one another which depends on the depth and length of the pack. The fixed folders have helical surfaces which extend longitudinally to the forming line so as to gradually fold the second flaps until they overlap the sheet of wrapping material, positioning them against the products. First sealing means are envisaged, for sealing the edges of the sheet of wrapping material which overlap underneath the pack; second sealing means are envisaged in the third station, for sealing the first and second flaps onto the sheet of wrapping material.
In the above-mentioned packaging machines, products are packaged in packs of various sizes, which make it possible to include different numbers of rolls in the packs, with various geometrical patterns. It is possible to make individual packs containing a single roll, and multi-roll packs containing two or more rolls. In the latter type of pack, the rolls may be arranged side-by-side to form a pack containing a single layer of products, or may be arranged to allow the packaging of packs with two or more layers of rolls placed on top of one another.
A disadvantage common to all types of known machines is the fact that, in order to set up the machine for packaging a pack size other than that currently in production, numerous adjustments are required, in particular, effected using several position references which are generally different, are separately controlled by the various physical machine parts and so require separate adjustments to be effected when passing from one type of pack to another. More specifically, adjustments to the operating stations are effected relative to the product sliding surface; in contrast, adjustments to the mobile lift table refer to the lowest level of the mobile table, said level being below the product sliding surface.
This means that the machine adjustment devices are of complex construction and require lengthy, complex machine adjustment and timing operations which also disadvantageously involve physical intervention on numerous devices, located in various zones of the machine.
The aim of the present invention is, therefore, to overcome the above-mentioned disadvantages by means of a machine which is able to allow the passage from one operating set-up to another, in terms of adjustment of both the pack size and configuration, with fewer adjustments than are needed on known machines, said adjustments also being more rapid and effected automatically in a centralized fashion, enabling the machine as a whole to meet rapidly changing market requirements for different types of packaging.
A further aim of the present invention is to obtain a machine with moving parts whose movements are more limited, the advantages of this being a reduction in the times required for the operating cycles and a reduction in the dynamic stresses.